I'm just getting started in photography, and would like to get a fairly inexpensive (less than $500, preferable less than $300) lens for my Nikon D40. I already know that I won't be able to find anything in this price range that will auto focus with my camera body, but that doesn't bother me. A few specific questions: I want a lens that will let me take shots of a wide range of subjects - portraits, flowers, as well as bees/bugs... is 90mm a good compromise, or should I get closer to 120mm? Should I stick with Nikon, or is Tamron/Sigma okay too (I've been looking at the Tamron AF90mm F/2.8 Di 1:1 Macro)? What's a good lens to get that will 'future proof' me if I decide to get a different camera body in the future that will auto-focus with a vast array of lens (such as a D90, D300, etc.)? Thanks!